Generation of carbon nanofilaments on carbon fibers at 550 °C

Employing a relatively new method, in which carbon structures are grown from fuel rich combustion mixtures using palladium particles as catalyst, multi-scale diameter nanometer – micrometer filament structures were grown from ethylene/oxygen mixtures at 550 °C on commercial PAN micrometer carbon fibers. The filaments formed had a diameter roughly equal to the palladium particle size. At sufficiently high metal loadings (>0.05 wt.%) a bimodal catalyst size distribution formed, hence a bimodal filament size distribution was generated. Relative short, densely spaced nanofilaments (ca. 10 nm diameter), and a slightly less dense layer of larger (ca. 100 nm diameter) faster growing fibers (ca. 10 μm/h) were found to exist together to create a unique multi-scale structure. A protocol was developed such that only nano-scale fibers or a mixture of nano and sub-micron fibers could be produced. No large range order was evident in the filaments. This work demonstrates a unique ability to create a truly ’multi-scale’ carbon structure on the surface of carbon fibers. This fiber structure potentially can enhance composite material strength, ductility and energy absorption characteristics.